644 SPECIAL SENSES 



fungiform papillae alone contain the organs of taste. Experiments on 

 the gustatory organs, by the application of solutions to different parts 

 through fine glass tubes, have shown that the mucous membrane around 

 a papilla has no gustatory sensibility, but that different savors can be 

 distinguished when a single papilla is touched (Camerer). 



In Fig. 159, which represents the dorsal surface of the tongue, the 

 large circumvallate papillae, usually seven to twelve in number, are seen 

 in the form of an inverted V, occupying the base of the tongue. The 

 fungiform papillae are scattered over the surface but are most abundant 

 at the point and near the borders. Both varieties of papillae are distin- 

 guishable by the naked eye. 



The circumvallate papillae simply are enlarged fungiform papillae, 

 each one surrounded with a circular ridge, or wall, and covered with 

 small secondary papillae. The fungiform papillae have each a short 

 thick pedicle and an enlarged rounded extremity. One hundred and 

 fifty to two hundred of these can easily be counted. These, also, pre- 

 sent small secondary papillae on their surfaces. When the mucous 

 membrane of the tongue is examined with a low magnifying power, par- 

 ticularly after maceration in acetic or in dilute hydrochloric acid, their 

 structure is readily observed. They are abundantly supplied with 

 bloodvessels and nerves. 



Several glandular structures are found beneath the mucous mem- 

 brane of the tongue. On either side of the frenum, near the point, is 

 a gland about three-quarters of an inch (20 millimeters) long and one- 

 third of an inch (8.5 millimeters) broad, which has five or six little open- 

 ings on the under surface of the tongue. Near the taste-buds, are small 

 racemose glands, which discharge a watery secretion by minute ducts 

 that open into the grooves within the walls of the circumvallate papillae 

 (Ebner). 



Taste-Buds. Loven and Schwalbe (1867) described under this 

 name peculiar structures that are supposed to be the true organs of 

 taste. They are found on the lateral slopes of the circumvallate papillae 

 and occasionally on the fungiform papillae. They consist of flask-like 

 collections of spindle-shaped cells, which are received into little excava- 

 tions in the epithelial covering of the mucous membrane, the bottom 

 resting on the connective-tissue layer. Their form is ovoid, and at the 

 neck of each flask is a rounded opening called the taste-pore. Their 

 length is ^\-^ to -^ of an inch (71 to 83 /*), and their transverse 

 diameter, about gl^ of an inch (41 /JL). The cavity of the taste-buds is 

 filled with cells, of which two kinds are described. The first variety, the 

 outer cells, or the cover-cells, are spindle-shaped and curved to corre- 

 spond to the wall of the beaker. These come to a point at the taste- 



